Introduction to Durability and In-Place Infiltration of Pervious Concrete
Charles Mitchell, P.E.
www.specializedengineering.com What is Pervious Concrete? NRMCA defines it….. www.perviouspavement.org
www.specializedengineering.com Pervious Concrete
From ACI 522R-10 Report on Pervious Concrete: concrete, pervious—hydraulic cement concrete proportioned with sufficient interconnected voids that result in a highly permeable material, allowing water to readily pass.
www.specializedengineering.com What is Pervious Concrete?
A Concrete producer defines it as:
No-Fines Mix
Low water/cement Ratio
Delivery and Placement A Design Professional defines it:
Intended for use as an open-graded drainage material
Capable of handling a given traffic load
Beneficial to the environment
www.specializedengineering.com What is Pervious Concrete?
Because of the absence of sand, the void space is between 10% and 25% 100-120 lbs/ft³ unit weight Air void structure and unit weight are used as acceptance criteria
―it looks a bit like a rice cake‖
www.specializedengineering.com What is Pervious Concrete?
Pervious concrete is not a proprietary product; it is a "recipe" for concrete that can be made to order by any concrete batch plant. Pervious concrete is installed without rebar; the thickness is minimum 6 inches for most parking lot applications.
www.specializedengineering.com Applications …Recreation and Parks Pathways
Parking Lots
Critical Sites
Driveways
Erosion Control
Green house or Nursery… Any new development
www.specializedengineering.com Brambleton Public Safety Center Pervious Concrete Design Section
www.specializedengineering.com Test Methods for Pervious Concrete
Plastic Tests
ASTM C1688 Density and Void Content Hardened Sample Tests
ASTM C1754 Density and Void Content
ASTM C1747 Potential Resistance to Degradation In-situ Tests
ASTM C1701 Infiltration Rate
www.specializedengineering.com Desired In Place Properties Abrasion Resistance
Strong, dense surface Good curing Durable mix
www.specializedengineering.com Desired In Place Properties Durability
From ACI 522R-10 Report on Pervious Concrete: raveling—the wearing away of the concrete surface caused by the dislodging of aggregate particles.
www.specializedengineering.com ASTM C1747/C1747M-13
Standard Test Method for Determining Potential Resistance to Degradation of Pervious Concrete by Impact and Abrasion
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ASTM C1747/C1747M-13
Purpose: Evaluate the potential resistance to degradation by impact and abrasion of pervious concrete mixtures. Allows the comparison of the relative potential resistance to raveling of pervious concrete mixtures of varying proportions and raw materials. Note: Test method not for cores
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ASTM C1747/C1747M-13 Apparatus Balance Marshall hammer 4x8 cylinder mold LA Abrasion machine 1‖ Sieve Ruler
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ASTM C1747/C1747M-13 Procedure – Molding Cylinders Get C1688 density Calculate mass needed to fill 4x8 mold halfway Weigh out calculated mass in mold Drop mold 10 times on level, rigid surface from a height of 1‖
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ASTM C1747/C1747M-13 Procedure – Molding Cylinders (cont.) Use Marshall Hammer to consolidate sample to 4‖ height Cap to prevent moisture loss Prepare 3 specimens
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ASTM C1747/C1747M-13 Procedure – Curing Cylinders Initial curing similar to C31 Cure at 70-77°F until cylinders are 7 days old
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ASTM C1747/C1747M-13 Test Procedure Remove molds Weigh 3 cylinders Place 3 cylinders together in LA Abrasion machine with no charges for 500 revolutions Hand sieve on 1‖ sieve Weigh material retained on 1‖ sieve
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ASTM C1747/C1747M-13 Calculate Divide the mass loss by the original mass of the three cylinders and multiply by 100. Record the mass loss as a percentage of the original mass.
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Desired In Place Properties Percolation (Infiltration) Rate
From ACI 522R-10 Report on Pervious Concrete: percolation rate—the rate, usually expressed as inches per hour or inches per day, at which water moves through pervious concrete.
www.specializedengineering.com ASTM C1701/C1701M – 09
Standard Test Method for Infiltration Rate of In Place Pervious Concrete
www.specializedengineering.com ASTM C1701/C1701M – 09
Purpose: Determination of the field water infiltration rate of in place pervious concrete (surface) Restrictions: Does not determine if bottom of pervious concrete is clogged, and does not determine infiltration of underlying drainage layer and soil www.specializedengineering.com ASTM C1701/C1701M – 09 Apparatus
Infiltration ring - 12±½‖ diameter Balance Container – 5 gallons Stop Watch Plumbers Putty Water
www.specializedengineering.com ASTM C1701/C1701M – 09 Apparatus
www.specializedengineering.com ASTM C1701/C1701M – 09 Test Locations
3 tests for up to 25,000 sf Additional tests each 10,000 sf Minimum 3’ between test locations Don’t test if standing water on surface Don’t test within 24 hours of precipitation
www.specializedengineering.com ASTM C1701/C1701M – 09 Infiltration Ring Installation
Clean surface by brooming Apply plumbers putty on bottom of ring Place ring on pervious concrete surface Press putty into surface and around ring edge, use more putty if needed
www.specializedengineering.com ASTM C1701/C1701M – 09 Prewetting
Pour 8 lbs. of water into ring Maintain a head of ½‖ inside of ring Determine time from start until no free water is on surface Determine water quantity for test
40 lbs. if time is less than 30 seconds
8 lbs. if time is 30 seconds or more
www.specializedengineering.com ASTM C1701/C1701M – 09 Test
Start within 2 minutes of prewetting Record the weight of water to be used Pour water into ring Maintain a head of ½‖ inside of ring Determine time from start until no free water is on surface
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ASTM C1701/C1701M – 09 Calculate
퐾푀 I = in/h 퐷2∗푡
K = 126,870 (in.3s)/(lbh)
www.specializedengineering.com ASTM C1701/C1701M – 09 Report
Test locations Date Age of Pervious Concrete Prewetting time Amount of last rain Weight of water used for test
www.specializedengineering.com ASTM C1701/C1701M – 09 Report
Inside diameter of ring Time elapsed during test Infiltration rate Note retests if any
www.specializedengineering.com ACI 522R-10 Single-ring infiltrometer
www.specializedengineering.com Other Tests Subgrade Infiltration Testing (note: a rate less than 0.52in/hr acceptable for pervious) - Double Ring Infiltrometer, ASTM D 3385
www.specializedengineering.com Other Tests ASTM D3665, random core location ASTM C42, Coring, 3 cores/5,000 sf ASTM C174, Core Thickness, -½‖, +1½‖
www.specializedengineering.com Frequently Asked Questions
What if oil spills on the concrete?
Oil is actually contained in the pervious system. Microrganisms actually feed on it and they are biodegraded with time Can pervious become clogged? How do you fix it?
Pervious can be clogged by runoff from adjoining areas that contains fines. Routine sweeping and vacuuming can restore the porosity.
www.specializedengineering.com Frequently Asked Questions
Is pervious susceptible to freeze thaw environments?
If pervious is placed on sufficient stone, in Virginia enough to manage the 10 yr storm event, the concrete will be protected from ice formation. Furthermore, the cement paste can be air entrained.
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